Deflection yoke for use in electron-beam tubes of television receivers with rapid magnetic field change elimination

Abstract

A deflection yoke device for use in three-gun color picture tube of television receivers includes a pair of vertical deflection coils which are divided into barrel magnetic field production coil sections and pincushion magnetic field production coil sections. The yoke also includes a varistor that controls the flow of current for corrections of cross-misconvergence PQV and misconvergence S3V while suppressing or eliminating white rasters. More specifically, the pair of vertical deflection coils are subdivided into a series circuit of two barrel magnetic field production coil sections and another series circuit of two pincushion magnetic field production coil sections to which the varistor is connected. The varistor produces a barrel magnetic field in the center region of a display screen where vertical deflection current remains relatively small, while allowing a pincushion magnetic field to be created in the upper and lower peripheral sections thereof where the vertical deflection current increases. This eliminates rapid switching of the nature of the vertical magnetic field in nature from the barrel magnetic field to the pincushion magnetic field so that white rasters will no longer be generated on the screen.

What is claimed is: 
     
       1. A deflection yoke device comprising: a coil bobbin for being placed around a neck of a color picture tube of television receivers;   a combination of a horizontal deflection coil pair and a vertical deflection coil pair for producing a magnetic field for deflection of one or several electron beams from the neck of the color picture tube;   said vertical deflection coil pair being divided into a plurality of barrel magnetic field production coil sections and a plurality of pincushion magnetic field production sections;   said barrel magnetic field production coil sections being connected in series to each other to provide a first series circuit;   said pincushion magnetic field production coil section being connected in series to each other to provide a second series circuit which is connected in parallel with said first series circuit; and   a voltage-dependent variable resistor connected in series to one of the first and second series circuits.   
     
     
       2. A deflection yoke device comprising: a coil bobbin for being placed around a neck of a color picture tube;   an assembly of a horizontal deflection coil pair and a vertical deflection coil pair for producing a magnetic field for deflection of one or several electron beams from the neck of the color picture tube;   said vertical deflection coil pair being divided into a first series combination of barrel magnetic field production coil sections and a second series combination of pincushion magnetic field production sections; and   a current control device connected in series to one of the first and second series combinations and including a resistive element including a varistor and having a resistance which varies with variations of a voltage applied thereto for forcing current flowing therein to change with variations in vertical deflection current supplied to said vertical deflection coil pair.   
     
     
       3. The device of claim 2, wherein said current control device prevents current to flow into said one of said first and second series combinations associated therewith when the vertical deflection current is less than a predefined level. 
     
     
       4. The device of claim 3, wherein said current control device allows current to flow in said one of said first and second series combinations when the vertical deflection current is greater than the predefined level while permitting flow of current in the other of said first and second combinations. 
     
     
       5. The device of claim 4, wherein when the vertical deflection current is greater than the predetermined level, said current control device allows the current flowing in said one of said first and second combinations to gradually increase as the vertical deflection current increases.